Recommended Settings for Routing Protocol Timers During Unified ISSU

You can use the default values for many of the routing protocol timers with no adverse effect on a unified in-service software upgrade. For other timers, we recommend particular values, as described in Table 22.

Table 22: Recommended Routing Protocol Timer Settings

Protocol

Timers

BFD

Use the default timers.

BGP

Use the default timers, including graceful restart default timers. If the expected forwarding outage for the platform is beyond what the BGP session’s graceful restart mechanism can survive, the unified ISSU initialization process generates a warning message accordingly. In this event, adjust the timer intervals as advised by the message.

For information about the expected forwarding outage, see Interruption in Traffic Forwarding for Layer 3 Routing Protocols During Unified ISSU.

DVMRP

Use the default timers.

IGMP

Use the default timers.

IS-IS

Use the default timers, including graceful restart default timers.

LDP

Use the default timers, including graceful restart default timers, except for the following:

  • Set the hello hold time to at least 901 seconds for a helper or a restarter configuration for a link-level adjacency or for LDP targeted sessions.

OSPF

Use the default timers, including graceful restart default timers, except for the dead interval.

If the expected forwarding outage for the platform is longer than the configured dead interval, the unified ISSU initialization process generates a warning message accordingly. In this event, adjust the timer interval as advised by the message.

For information about the expected forwarding outage, see Interruption in Traffic Forwarding for Layer 3 Routing Protocols During Unified ISSU.

PIM

Set the query interval to at least 210 seconds.

Unified ISSU generates a warning for any of the following conditions, but you can ignore the warning without causing a higher FC outage:

  • The current router is a DR.
  • The current router is configured as an Auto RP mapping agent and is chosen as the RP for any group.
  • The current router is an elected or candidate BSR, or if BSR candidate RPs are configured.
  • The graceful restart timer is less than the default value, 30 seconds.

RIP

Use the default timers; graceful restart is not supported. For scaled configurations, such as for 2000 RIP interfaces, use the following values:

  • Flush interval: 600 seconds
  • Holddown time: 260 seconds
  • Invalid interval: 260 seconds
  • Update interval: 60 seconds

RSVP-TE

Use the default timers, including graceful restart default timers, except for the following:

  • For graceful restart, the hello timeout interval is the product of hello misses multiplied by the hello refresh interval. Determine which period is longer, the IC upgrade time or the forwarding upgrade time. Configure the hello refresh and hello miss values so that the hello timeout is greater than the longer of those two periods.
  • For node hellos, the product of the refresh misses multiplied by the hello refresh interval must be great than the FC outage time. For an outage time of less than 30 seconds, for example, configure the following values:
    • Set the node hello refresh interval to 8000.
    • Set the node hello refresh misses to 4.

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